In recent years, an inorganic fine particle-dispersed paste composition, which is provided by dispersing inorganic fine particles such as electrically conductive powders, ceramic powders, and glass powders in a binder resin, has been used to obtain a fired body of various shapes. For example, an electrically conductive paste provided by dispersing electrically conductive powders in a binder resin has been used for formation of a circuit, production of a capacitor, or the like. Also, a ceramic paste or a glass paste provided by dispersing ceramic powders or glass powders, respectively, in a binder resin has been used in production of a dielectric layer of a plasma display panel (hereinafter, referred also to as PDP), a laminated ceramic capacitor, or the like.
A sintered body of the aforementioned kind of inorganic fine particle-dispersed paste composition in a desired shape is obtainable when the inorganic fine particle-dispersed paste composition is processed into a predetermined shape by, for example, screen printing, coating using a doctor blade, casting for sheet processing, or some other methods, and then fired. Screen printing is especially suitable for mass production among the exemplified methods.
Currently, ethylcellulose is often used as a binder resin for printing materials. An inorganic fine particle-dispersed paste composition for printing is printed on a substrate, and then heated and fired for thermal decomposition of the binder resin so as to provide a layer consisting of inorganic fine particles. However, the firing needs to be performed at high temperatures to prevent organic matters from remaining due to low thermal decomposition properties of ethylcellulose. Therefore, use of ethylcellulose unfavorably requires high production energy or takes a lot of time.
For the above reason, ethylcellulose has not been suitably used as a binder resin especially in the case where inorganic fine particles with low heat resistance are used.
On the other hand, Patent Document 1 discloses a paste composition containing an acrylic resin with excellent thermal decomposition properties. The inorganic fine particle-dispersed paste composition containing the acrylic resin can be fired at low temperatures in a short time because of the excellent thermal decomposition properties of the binder resin.
However, even this kind of binder resin needs to be decomposed at a still lower temperature when used in combination with some kinds of inorganic fine particles including a low-melting-point glass such as bismuth oxide having a softening point of 400° C. or lower, electrically conductive fine particles of copper, and silver, which are easily oxidized in sintering, or the like.
In light of the aforementioned problems, examinations have been conducted recently on use of a polyether-based resin such as a polyether resin and an acrylic resin having a polyether side chain as a binder resin. However, when any of the above resins is used as a binder resin, the composition to be obtained can have a sufficient viscosity only when a large amount of the resin is mixed therein. Therefore, the composition ratio of the resin needs to be high in the inorganic fine particle-dispersed paste composition.
Furthermore, although the polyether-based resin is thermally decomposed at a relatively low temperature of 400° C. or lower, since soot generated upon combustion of the ether structure is adsorbed on the surface of the inorganic fine particles and thus a large amount of residual carbon remains in the sintered body to be provided after sintering, it is impossible to take full advantage of the properties of the inorganic fine particles.
Patent Document 1: Japanese Kokai Publication No. Hei-11-71132 (JP-A H11-71132)